The Biocontrol of Gorse, Ulex europaeus, in Chile: A Progress Report

Gorse, Ulex europaeus, has become the most important weed of silvicultural and rangeland industries in Chile. The earliest attempt to control it biologically was made in 1976 when the seed predator Apion ulicis was introduced into the country. This bioagent established successfully throughout the gorse infested areas but has not been able to reg- ulate the weed on a national bases by itself. The program was renewed in 1996 which resulted in the introduction, quarantine, host-testing, rearing and release of two addition- al bioagents; the gorse spider mite, Tetranychus lintearius (Acari: Tetranychidae) and the gorse shoot-tip moth, Agonopterix ulicetella (Lepidoptera: Oecophoridae). Two gorse spider mite populations introduced from Hawaii and Portugal were released in 1997. They are now colonizing gorse stands and increasing their densities at over 50 sites between the 37° and 40° parallels of southern latitude, especially at the Chilean most important silvicultural areas. The gorse shoot-tip moth, introduced from Hawaii and the UK was first released in Chile in 1997. This bioagent successfully over- wintered at nine sites between the 38° and 40° parallels of southern latitude. The best col- onization of the population collected at Hawaii occurred at gorse stands located in warmer, drier areas of Chile, whereas the UK population performed better in humid areas.